Magnetic strips or magnetic rings with at least two alternating north and south poles are used for a contactless position measurement of linear, moved or rotating parts. These magnetic strips or rings are then firmly connected to the moved parts and are moved at a small distance over a magnetic field sensor. If a precise position measurement in a specific resolution is required, the magnetic field sensor can also consist of an array of several individual sensors. One can thereby make use of the fact, for example, that the vertical magnetic field component has a sine-shaped curve over the magnetic strip.
For the position determination, the sensors can be placed in such a manner that the sine-shaped field curve is measured on at least two sites with a distance corresponding to one-fourth of the length of the pole pair, which corresponds to a phase difference of 90° in the field curve. Thus, signals shifted 90° with respect to one another are produced. The actual position determination is regularly carried out in this case by means of a ratio determination of these two signals and the utilization of angle functions. An absolute position of the magnet source can be determined hereby within the measured pole pair.
With such a method, however, static magnetic fields can influence measured signals in such a way that a position determined from the signals is fraught with errors. Moreover, an arrangement in which corresponding magnetic field sensors are arranged at a stationary distance to one another can be used only with magnet sources of a pole length determined by this distance. Since the position determination is carried out as an absolute value only in the area of the length of a pole pair, the absolute measurement range is also limited with traditional arrangements of this type.